At the bottom of the Treporti Channel, meters beneath the waves of the Venetian Lagoon, a series of surprising ancient structures has just been uncovered.

Aligned for a distance of around 1,200 meters (3,937 feet), they suggest that, once upon a time, before sea levels rose and flooded the area, a Roman-era road stretched across the landscape.

According to archaeologists, this is evidence that a significant Roman settlement was present centuries before the founding and settlement of Venice in the fifth century CE.

"This multidisciplinary study documented the presence of an about 1,200-meter long segment of a submerged Roman road on an ancient beach ridge now submerged in the Northern Venice Lagoon," a team of archaeologists led by Fantina Madricardo of the National Research Council of Italy explains in a new study on the discovery.

010 venice 2(Antonio Calandriello and Giuseppe D'Acunto; Fantina Madricardo)

Above: A reconstruction of the road (left), and how the channel looks today (right).

"The submerged road represents, probably, one of the last route segments in the maritime landscape of Altinum, within a wider network of roads in the Venetia et Histria Regio," the researchers write.

"Its contiguity with other structures and infrastructures, such as … defensive towers, levees-walkways, port, and private structures, confirms the capillary permanent settlement in the Venetorum angulus."

The ancient Romans did many things very well. Among those things, one of the most well-known is their roads. Wheresoever the Romans roamed, there too you would find long stretches of pavement and corduroy roads, to better facilitate expansion and mobility.

But Roman transportation and trade was not limited to land. The ancient civilization was also adept at navigating the seas, which led researchers to wonder what role the Venice region may have played.

We know the sea level was lower then, and Venice would have looked significantly different. Archaeologists have also found ancient artifacts that suggest Roman occupation in the centuries around the turn of the millennium, long before the city of Venice was founded. How extensive, Madricardo and her team wondered, was that occupation?

Some archaeologists had believed that the artifacts had come from ancient Roman cities overlooking the lagoon, but there were also hints that the area had been more extensively occupied.

A survey conducted in 1985 found structures that suggested evidence of stretches of road at the bottom of the Treporti Channel.

High-resolution multibeam sonar allowed the researchers to map the seafloor geomorphology, and archaeological dives conducted between 1978 and 2016 returned a wealth of information about what's actually down there, including sample cores of the seafloor sediment.

structuresBathymetric map showing the locations of the structures. (Federica Foglini)

With further studies in 2020, they documented a series of 12 relief structures aligned parallel to the main channel in a southwest-to-northeasterly direction, for a distance of around 1,140 meters (3,740 ft). The longest of these structures was around 52.7 meters long. A second set of four structures ranged between 14.5 and 134.8 meters (47.5 to 442 ft).

Bathymetric data suggested the presence of a paleobeach ridge - a feature indicative that a beach had existed at some point in the past. The structures were found along this ridge.

The existence of a road is supported by other discoveries in the channel. Multiple archaeological traces have been previously found near the Scanello Channel; these traces suggest large buildings, which could indicate the presence of a harbor.

Previous research also suggested traces of a road at the bottom of the Scanello Channel, too. If that's the case, then the Treporti Channel road would not be an isolated structure, but part of a larger road network in a significant port town.

Comparison with other submerged ruins in the Lagoons of Grado and Marano support this interpretation of the structures. The findings highlight the need to find, document, and preserve archaeological sites in submerged environments, the researchers say.

"The presence of the ancient Roman road confirms the hypothesis of a stable system of Roman settlements in the Venice Lagoon," they write in their paper.

"The study highlights the significance of this road in the broader context of the Roman transport system, demonstrating once more the Roman ability to adapt and to handle complex dynamic environments that were often radically different from today."

The research has been published in Scientific Reports.